The Elusive Lightning Sprites -
This Week in Space

The Israeli disappointment in the AX-2 mission

The second private mission to the International Space Station, AX-2, was successfully completed this week, with the Dragon spacecraft landing in the Gulf of Mexico on Tuesday night. The four crew members, Commander Peggy Whitson, Saudi astronauts Rayyanah Barnawi and Ali Alqarni, and private astronaut John Shoffner, spent ten days in space as planned. They conducted a series of scientific experiments, but disappointingly, the Israeli experiment was not conducted.

The team was supposed to continue the ILAN-ES experiment, which had been very successfully completed during the AX-1 mission, as part of the Rakia mission of Israeli astronaut Eytan Stibbe. In the experiment, led by Professor Yoav Yair from Reichman University, Stibbe photographed lightning sprites – colorful and dazzling light flashes tens of kilometers in size that appear in the blink of an eye above the clouds during lightning storms. But due to their extremely short duration of only a few thousandths of a second, capturing and studying these sprites is very challenging.

Yair and his colleagues developed methods to accurately forecast when and where suitable lightning storms for capturing will occur, and also determined how to align photography targets with the transit times of the spacecraft or the space station overhead. This precision enabled them to instruct the astronauts exactly when and where to attempt to capture images of the lightning sprites, along with other transient atmospheric phenomena. This method had been successfully implemented already during the flight of the first Israeli astronaut Ilan Ramon aboard the Columbia Space Shuttle in 2003, and has since been repeated by astronauts on the space station.

I am phenomenally disappointed," Yair told the Davidson Institute's website. "I worked for hours every day to provide them with targets, and day after day I received a message that the photograph was not taken. However, in the end, I view this as a gift. This experiment was not initially planned, and Rakia company promoted it as part of their collaboration with Axiom. Therefore, I conducted the scientific work, further improved the methods and we will attempt it again next time".

According to Yair, the original plan was for Shoffner to take the photographs, but NASA ultimately did not allow the experiment in the proposed format. Then Stibbe persuaded mission commander Peggy Whitson to undertake the photography attempts. "There was a feeling that it was going to happen. We even had a Zoom call with the entire team, including the Saudis, trained them on the experiment and Eitan explained how he took the photos. There was a feeling that it was going to happen, but I didn't even get a single photo", summarized Yair.

"Unfortunately, they did not manage to photograph any lightning storm, even though they tried", said Melody Korman, Space Operations Manager at Rakia. "They had much less time for the experiment compared to AX-1, as it was a shorter mission, and it didn't work out. But this experiment is expected to go back to space on their next mission, AX-3, planned for November this year".

The mission came to an end, but without any sprites. The Dragon spacecraft makes its way to the recovery ship, shortly after landing in the Gulf of Mexico | Photo: SpaceX via Twitter

Seventeen Individuals Simultaneously in Orbit

While it was only for a brief time, a new record was set this week for the number of people simultaneously orbiting the Earth, reaching 17 individuals. On Tuesday, as the four-member team of the private mission AX-2 departed from the International Space Station heading back to Earth, China launched an additional team of taikonauts to their space station, Tiangong 3. At that moment, there were seven crew members at the International Space Station, four team members of AX-2 in the Dragon spacecraft, and the two Chinese teams at their station – three taikonauts who arrived at the station last week and three who will soon leave it. This breaks the previous record, set in 2021, when 14 people were in orbit around the Earth.

Suborbital flights, if considered alongside those found in Earth's orbit, would push the record for the total number of people in space even further, briefly reaching 20, during the flight of Virgin Galactic, which takes tourists to the edge of space. After a lengthy hiatus, the company resumed its flights on May 25, with their spacecraft, VSS Unity, reaching a maximum altitude of approximately 87 kilometers, which by the American standards is already considered a space flight. The inaugural renewed flight included two pilots and four senior company employees, and later this month, they are expected to resume commercial flights.

Six out of 17. The two teams of Shenzhou 15 and 16 missions at the Chinese space station this week | Photo: China Manned Space Agency

North Korea's Failure

After weeks of anticipation, North Korea finally launched its new military reconnaissance satellite this week. The launch started promisingly and the first stage of the missile performed well, but a malfunction occurred during the second stage, causing the satellite vehicle rocket to crash into the sea along with the satellite it carried. "Official North Korean statement on the launch failure is unique. To me it represents a step forward in that acknowledging failure is a sign of maturity of the program.” said space analyst Tal Inbar, a senior research fellow at the American MDAA (Missile Defence Advocacy Alliance) organization, missile and air defense research, specializing in North Korea's space and missile programs.

Despite the relative transparency shown by Pyongyang, little is known about the satellite and its launch vehicle. More information may be gleaned from parts of the first stage that the South Korean military retrieved from the sea, images of which have been widely published. "This is a new launcher, an extension of North Korea's ballistic missile program. It's unclear whether it's a two-stage missile or if it has a small third stage intended to position the satellite in its orbit. We might glean more information if the second stage and the satellite itself, or parts thereof, are recovered from the sea," Inbar added. "The launch was also conducted from a new facility within the launch site previously used for previous attempts."

Following the unsuccessful attempt, North Korea announced plans to retry the satellite launch, although naturally, no specific date has been set. "It's uncertain whether they manufactured two satellites and two launchers in advance," Inbar clarified. "However, based on my knowledge of their operations, it's highly likely that we will witness another launch attempt later this year."

The first stage landed in their grasp. Parts of the launch missile’s first stage, salvaged from the sea by South Korea | Photo: South Korean Ministry of Defense

The Folding Shield

The UK-based company Space Forge is set to conduct a trial this year involving a groundbreaking heat shield that promises to allow safe reentry of spacecraft and satellites to Earth. Upon returning from Earth's orbit or longer distances, spacecraft enter the atmosphere at high speeds, resulting in friction with the air that converts some of their kinetic energy into heat, which could potentially incinerate them. The majority of spacecraft are equipped with an ablative heat shield made of disposable materials that burn and dissipate some of the heat. However, this type of shield can only be used once and must be replaced after each mission if the spacecraft is intended to be reusable.

The shield developed by the British company works differently. Made of heat-resistant alloys and possessing a large internal surface area, the shield is capable of diverting the heat away from the spacecraft and ultimately radiating it into the atmosphere, enabling the shield to be reused multiple times. The shield is typically stored in a compact, folded state and unfolds, much like origami, as it nears reentry.This maximizes surface area for efficient heat transfer, while also ensuring that it can be launched in its compact form.

According to the company, the heat dissipation and large surface area of the shield significantly decelerate the spacecraft's descent, making parachutes unnecessary. Instead, they propose retrieving the spacecraft close to the ground using a specialized net. Dubbed Pridwen, after King Arthur's legendary shield, the heat shield is set for its first test this year, as part of a mission by SpaceX. The folding shield will be launched as a secondary payload on a Falcon 9 rocket, descend back to Earth, and deploy before entering the atmosphere, in order to assess its performance.

This experiment, supported by the European Space Agency, joins a project by an American company to develop an inflatable heat shield. After years without notable advancements in this field, it appears that the space industry has recognized the value and potential of such technologies, not just for Earth reentry, but also for missions to other planets with an atmosphere, such as Mars.

The folding heat shield technology could even obviate the need for parachutes. Space Forge's heat shield | Illustration: ESA/Space Forge

Saturn's Surprising Faucet

Enceladus, one of Saturn's moons, captivates researchers due to its intriguing characteristics. It harbors an ocean of liquid saltwater between its outer ice shell and inner core, occasionally spewing water geysers through cracks in the ice. The Cassini spacecraft, which extensively studied the Saturn system, managed not only to photograph these geysers, but even to venture through the steam plumes of these geysers, which can reach hundreds of kilometers in height, providing insights into their composition.

Recently, scientists, using the James Webb Space Telescope, managed to photograph one of Enceladus' geysers and were surprised to discover a massive water plume, stretching around 10,000 kilometers. “When I was looking at the data, at first, I was thinking I had to be wrong. It was just so shocking to detect a water plume more than 20 times the size of the moon,” said lead author Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said Gerónimo Villanueva, the research team lead at NASA's Goddard Space Flight Center in Greenbelt, Maryland.“The orbit of Enceladus around Saturn is relatively quick, just 33 hours. As it whips around Saturn, the moon and its jets are basically spitting off water, leaving a halo, almost like a donut, in its wake,” added Villanueva. 

The telescope's sensitive measuring devices allowed the researchers to calculate the rate of water emission, revealing an estimate of about 300 liters per second, significantly surpassing previous estimates. Data analysis showed that about 30 percent of the water emitted from the plume remains in that steam ring, while the remaining 70 percent disperses throughout the Saturn system and may even reach its rings. In the coming years, the scientists plan to continue studying Enceladus with the space telescope, and also examine other moons where liquid water likely exists. The aim is to better understand these celestial bodies, including aspects such as the thickness of their outer ice layers, in preparation for plans to land robotic missions designed to reach the water bodies directly.

A ring of water vapor. Simulation of the water's path in Enceladus' orbit, and the data from the measurements of the space telescope | Source: NASA, ESA, CSA, STScI, Leah Hustak (STScI)